基于AVL-BOOST的可变正时汽油机泵气损失研究

Research on pumping loss of variable timing engine based on AVL-BOOST

利用BOOST软件建立一款自然吸气四缸汽油机的仿真模型,可变气门正时汽油机通过可变液压气门机构实现进气门开启持续期和进气早关角的连续可变.将实测的气门运动数据按照不同的负荷要求输入模型,由于取消了节气门,进气节流阀R1取值为1.进气早关角依次设定为原机进气晚关角之前的6~56°CA,以10°CA为一间隔,研究不同转速下的充量系数变化趋势.结果表明:可变正时汽油机低速时,选择较大的进气早关角可避免进气倒流,高速时选择较小的进气早关角可充分利用过后充气,兼顾了高低速工况的进气性能.根据传统汽油机和可变正时汽油机负荷调节方式的不同设定两种仿真模式,传统汽油机配气定时固定不变,进气节流阀R1取值0~1之间某值以模拟不同的节气门开度,可变正时汽油机输入不同进气早关角的气门升程数据,匹配两种模式下的平均有效压力值相同,对比不同转速下泵气损失随负荷的变化趋势.结果表明:可变正时汽油机相比于传统汽油机对降低泵气损失有明显优势,低转速小负荷时改善程度最明显,最多可降低泵气损失约49%;高转速大负荷时改善程度最弱,全部实验工况下平均降幅约为34%.

A simulation model of four cylinder engine using BOOST software was established,variable timing gasoline engine with variable hydraulic valve mechanism to achieve the continuous period of the valve opening and continuously variable inlet early angle.According to different load requirements,measured valve lift data was entered into the model,since the cancellation of the throttle,the intake throttle valve R1 value of 1;Setting different inlet angle and comparing the change trend of the filling coefficient under different speed.The results showed that variable timing engine at low-speed select larger intake early off angle could avoid inlet backflow and high-speed select smaller intake early off angle could make full use of the inertia air intake,the intake performance of both high and low speed conditions was considered.The throttle valve of traditional engine was set with different opening degree,and the variable timing engine input different valve lift data to meet the same BMEP value,the trend of pumping loss at different speed with the change of engine load was calculated.The results showed that the variable timing engine had obvious advantages in reducing the pumping loss,especially when low speed and small load was more obvious.